Heating pad and a process for making same



Aug. 5, 1941. G. VAN DAAM ETAL.

HEATING PAD AND A PROCESS FOR MAKING SAME Filed June 29, 1938 Gem? 2/2?31 EH71) 5 Trans Z/Qj aha/5W ATTO \NEY.

Patented Aug. 5, 1941 HEATING PAD AND A PROCESS FOR MAKING SAME GerritVan Daam, Bufialo, N. Y., and Emil Stranszky, Erie, Pa., assignors toNorth American Electric Appliance Company, 1110., Buffalo, N. Y., acorporation of New York Application June 29, 1938, Serial No. 216,544

((31. Zia-46) 2 Claims.

'lhis invention relates generally to electrical heating elements andmore particularly to electric heating pads.

In the manufacture of electrically heated pads, it is customary to windthe resistance wire hell cally around a core and finish it with a rowingor yarn outer cover Or insulation. This resistance element is affixed toa heat resistant cloth or web hing which in turn is enclosed in an outerwoolen or fabric cover. In order to make these pads water andmoistureprooi, it is customary to enclose these pads in a rubber bag.These rubber bags are very stiff and do not stand any hard usage therebymaking them very short lived. These rubber bags are likewise notrepairable and they are easily punctured by pins and the like. The yarnwhich is used to insulate and cover the resistance wire in the padbecomes distorted and unraveled and. the fibers of the yarn aredismembered and torn loose from the close weaving of the insulated wirewhen it is woven into a pad. In covering the resistance wire itself,great tensional force is necessary in order that the wire may beinsulated and this results in the breaking of the fibers of the yarnused for covering. The resultant heating pad produced by the old methodhad many weak spots as well as a number of spots which had theinsulation torn oil. The appearance of the pad was likewise unsightlybecause of the fringe or projecting fibers apparent on all portions ofthe Dad. These prior pads were not waterproof. The use of glass yarn inthese prior pads was impractical because there are at least 200 fibersin one strand of glass yarn and these would unravel or break upon closeweaving or winding of the yarn. Glass yarns will notwithstand the heavytensional forces placed upon them during the winding and weaving of theyarn and the friction resulting from the winding and weaving operationsnecessary breaks the fibers and leaves a pad which is weak,unsightly inappearance because of the projecting frizzled fibers, and poorlyinsulated. A pin or any sharp instrument may be injected into theseclothes or yarns causing electrical shock to the.

patient using it and thereby making these prior pads a danger when usedwith sick patients.

These prior pads were not safe because of the fire hazard created when aresistance wire broke. Body perspiration and uric acid very quicklydeteriorated these prior pads.

It is, accordingly, an object of our invention to overcome the above andother defects in heating pads and more particularly to provide a heatingpad which is efilcient and safe in operation,

cheap in cost, water and airproof, easy to repair, and maximum in life.

Another object of our invention is to provide a heating pad which has asmooth exterior surface.-

Another object of our invention is to provide a means permitting the useof glass or other noninflammable yarns in the manufacture of heatingpads.

Another object or our invention is to provide a heating pad which.prevents injection of a pin or sharp instrument thereby preventingelectrical shocks to the person using the pad.

Another object of our invention is to provide a heating pad which willautomatically extinguish arcs produced by the resistance wires therebyeliminating a fire hazard.

Another object of our invention is to provide a heating pad which iswater and airproof without the use of a rubber hag.

Another object of our invention is to provide a process whereby glass orother non-inflammable yarns may be used in the manufactureof heatingpads and the like.

Other objects of our invention will become evident from the followingdetailed description, take in conjunction with the accompanying drawing,in which Fig. l is a side elevational view with parts broken away of ourinsulated resistance wire made according to our process.

Fig. 2 is a fragmentary view of a heating pad wherein the insulatedresistance wire is woven in with other non-inflammable yarn.

Fig. 3 is a fragmentary view of a heating pad in which the resistancewire is disposed between fabric cloths or the like of glass or othernon-inflammable material.

Fig. 4 is a fragmentary view of a heating pad having resistance wiressecured to a fabric cover or the like.

In the manufacture of an insulated resistance wire for use in heatingpads and the like using glass or other non-inflammable yarn of a.fibrous nature for the insulating covering according to our invention,one'form of which is shown in Fig. 1, a core I has a resistance wire 2wound therearound over which glass or other non-inflammable fibrous yarn3 is wrapped or wound. The whole insulated wire has applied thereto aviscid material 4 which hardens upon exposure to air. This viscidmaterial combines with the fibers of the yarns 3 and bindsthem togetherto make the whole insulated wire strong and durable enough to use forany purpose. It is in,- tended to weave the whole insulated wire withother glass or non-inflammable fibrous yarn as shown in Fig. 2 althoughthis insulated wire may be used in many other combinations. In Fig. 3the insulated wire 6 is secured between two fabric cloths 1 and 8 ofglass or other non-inflammable material. Fig. 4 shows a resistance wirel0 secured to a fabric cloth or pad 9 made of glass or othernon-inflammable material.

When the yarn 3 is wound or wrapped over the core I, it is evident thata great tensional force is necessary to perform this operation and muchfriction exists. It has been found that glass or other non-inflammablefibrous material cannot be used for the yarn covering to produce apractical and workable bag since a bag made from this yarn is weak,unsightly in appearance, and the fibers of yarns are frayed from theweaving and winding. By applying the viscid material 4, the yarn may beclosely woven or wound without a single fiber of the yarn becomingfrayed, broken, or dismembered. The application of this material alsorenders the insulated wire fireproof, waterproof, and shockproof. Whenglass yarn is used, which is the usual case, no pin can be injected intoit as in the pads now on the marlret and therefore no shock can betransmitted to the patientusing the pad. Another important item in theuse of glass yarn for heating pads is the safety from fire upon breakingof the resistance wire. With the use of glass yarn, the wires will notcause an are because the glass will melt and smother the areimmediately. After the resistance wire is woven into a webbed pad withother glass or non-inflammable yarn, the whole pad is again subjected toan application of the viscid material which hardens upon exposure toair. It will be understood that thecore i may be dipped into the viscidmaterial before or after the resistance wire is wound thereon if this isdesired without departing from the spirit of the invention. It will befurther understood that any form of resistance wire may be used audit isnot necessary that a core be used.

It will be evident from the above that any of the difierentconstructions of heating pads may be utilized with the resistance wireas shown in Fig. 1. In all of these constructions, the resistance wirewith the glass or other non-inflammable fibrous yarn wound therearoundis first combined with a material of a viscid nature which hardens uponexposure to air and when this insulated resistance wire is woven orotherwise secured to a pad or fabric, the whole pad is again dipped intothe viscid material. The pad is thereby rendered waterproof, acidproof,airproof, and shockproof.

The material which has been found most desir able for binding andotherwise strengthening the fibers of the glass or other non-inflammablefibrous yarn in our heating pads is a specially processed rubber latex,or artificial rubber latex, which is a viscid liquid and attains acertain hardness upon exposure to air. A viscid varnish which hardensupon exposure to air has also been used for this purpose.

It will be apparent from the foregoing description that we have produceda heating pad which is fireproof, waterproof, shockproof, airproof, andotherwise durable besides being resistant to uric acid and bodyperspiration. It is the only method by which glass or othernoninflammable fibrous yarn may be used in a heating pad with any degreeof safety, comfort, and practicability,

Various changes may be made in the specific embodiment of the presentinvention without departing from the spirit thereof, or from the scopeof the appended claims.

What we claim is:

1. A flexible, water-proof, acid-proof, fireproof, shock-proofelectrical heating pad resistant to puncture by sharp or pointedinstruments comprising a core, resistance wires wound around said core,a fibrous glass yam wound around said core for covering said resistanceWires, a fibrous yarn into which said fibrous yarn covered resistancewires are woven, a latex compound covering the fibrous yarn coveredresistance wires, and a second coating of latex compound covering thewhole heating pad, the said latex compound being hardened upon exposureto air. 2. A method of manufacturing a flexible, wa-

ter-proof, fire-proof, acidproof, shock-proof electrical heating padcomprising the winding of a resistance wire on a core, covering saidcore and resistance wire by winding a fibrous glass yarn therearound,coating said core, wire, and yarn with a latex compound which hardensupon exposure to air, weaving said resistance wire into a yarn pad andcombining said woven pad with a latex compound which hardens uponexposure to air. I

GERRIT VAN DAAM.

EMIL STRANSZKY.

